1. Field of the Invention
The present invention relates to apparatuses and methods for producing an electron source and, more particularly, relates to an apparatus and method for producing an electron source having electron emitters.
2. Description of the Related Art
Known electron emitters are broadly divided into two types: thermionic emitters and cold cathode emitters. Examples of cold cathode emitters include field emitters (hereinafter referred to as FEs), metal-insulator-metal emitters (hereinafter referred to as MIM emitters), and surface-conduction electron emitters.
Examples of known FEs include those disclosed in W. P. Dyke and W. W. Dolan, “Field Emission,” Advances in Electronics and Electron Physics, 8, 89 (1956) and C. A. Spindt, “Physical Properties of thin-film field emission cathodes with molybdenum cones,” J. Appl. Phys., 47, 5248 (1976).
An example of known MIM emitters is disclosed in C. A. Mead, “Operation of Tunnel-Emission Devices,” J. Appl. Phys., 32, 646 (1961).
An example of surface-conduction electron emitters is disclosed in M. I. Elinson, Radio Engineering and Electron Physics, 10, 1290 (1965).
Surface-conduction electron emitters utilize a phenomenon in which electrons are emitted by supplying a current across the surface of a small, thin film formed on a substrate. For example, Japanese Patent Laid-Open Nos. 7-235255 and 8-171849, assigned in common with the present application, have proposed novel surface-conduction electron emitters and their application and have disclosed their fundamental structures and manufacturing methods.
According to a typical example of such surface-conduction electron emitters, an electron-emission part is formed on a thin conductive film connected between a pair of device electrodes provided on a substrate by an electrifying process called an energization forming process, in advance, and a subsequent activation process.
The energization forming process is a process of forming a slit having high electrical resistance by applying a voltage across the thin conductive film to break, deform, or modify the film locally.
The activation process is a process of forming a carbon film in the vicinity of the slit by applying a voltage across the thin conductive film in a vacuum atmosphere containing an organic compound. Electrons are emitted from the vicinity of the slit.
Surface-conduction electron emitters, which have a simple structure and are easy to produce as described above, have the advantage that a large number of the devices can be arrayed over a large area. Various applications have therefore been studied to exploit this feature. Examples of such applications include image-forming apparatuses such as charged particle beam sources and displays. An example of applications in which many surface-conduction electron emitters are arrayed is an electron source on which many lines of surface-conduction electron emitters connected in parallel are arrayed.
According to known methods for producing surface-conduction electron emitters, it is effective for improving device characteristics that devices including a pair of electrodes and a conductive film are placed in a vacuum atmosphere, are subjected to the energization forming process, and are supplied with properly selected voltage pulses for several minutes to tens of minutes after the introduction of a gas containing at least one common element with a deposit to be formed on the electron-emission parts into the vacuum atmosphere (the activation process). The activation process improves the characteristics of electron emitters, that is, significantly increases electron-emission current Ie relative to voltage with its threshold maintained.
This activation process, however, has the following problem.
The activation process, in which carbon or a carbon compound is deposited on and around the electron-emission parts, involves the decomposition of an organic compound adsorbed on the device substrate in the atmosphere. A larger number of devices subjected to the activation process at the same time therefore results in a larger amount of organic material decomposed and consumed per unit of time. Such a larger consumption of organic material may vary the concentration of the organic material in the atmosphere, decrease the rate of forming a carbon film, and cause variations over the surface of the substrate, thus impairing the uniformity of the resultant electron source.